Isotopic studies of leaf water. Part 2: Between-age isotopic variations in pine needles

The enigma of effective path length for 18O enrichment in leaf water of conifers

“…; Shu et al . ), though in these studies, younger age classes were less enriched than older. In some of these studies with pine needles, the comparisons were made between mature needles produced in different years rather than developmental changes within a single year.…”

Isotopic studies of leaf water. Part 1: A physically based two-dimensional model for pine needles

“…One may argue that a differs between a young growing needle and a fullgrown one (see Shu et al, 2008), but no information is available to explain a variations among full-grown needles. It is possible that a may be species-dependent, being higher for red pine than for white pine (see more data in Shu et al, 2008). Obviously, this is an important area of future investigation for understanding leaf water isotopic variations.…”

“…The objectives of this paper and its companion (Shu et al, 2008) are (1) to investigate how the isotopic composition of leaf water in pine needles varies within a single leaf along the water transport path, and how that isotopic variation is affected by environmental parameters as well as leaf physiological factors; (2) to understand how within-leaf isotopic variations affect the measured bulk leaf water, and (3) to evaluate whether simple isotopic models are adequate for calculating leaf water under a wide range of environmental and physiological conditions. In this first paper of the pair, we describe a 2D model for simulating within-leaf steady-state isotopic distributions of pine needles, and then use the model to simulate observations from two pine species, Pinus resinosa Ait and Pinus strobus L. We also evaluate the accuracy of the boundary layer model, using this 2D model and published leaf water data.…”

A single‐substrate model to interpret intra‐annual stable isotope signals in tree‐ring cellulose

“…Similar differences in Δ 18 O lw have been reported in other species. Allison, Gat & Leaney (1985) observed, in the summer but not in spring, significant differences of leaf water enrichment in P. radiata with position and needle age, whereas Shu et al. (2008) found that current‐year needles were less enriched than previous‐year needles in P. resinosa and P. strobus , but that the difference between the two cohorts of needles progressively weakened as young needles matured.…”

“…(2008) found that current‐year needles were less enriched than previous‐year needles in P. resinosa and P. strobus , but that the difference between the two cohorts of needles progressively weakened as young needles matured. This was attributed to differences in transpiration rate patterns along the needles (Shu et al. 2008).…”